Multi-chip packaging structure having chips sealably mounted on opposing surfaces of substrates

ABSTRACT

In a method for manufacturing an electronic apparatus, an electronic component is mounted on an organic substrate within its cavity. The electronic component is sealed by a concave molded resin enveloper filled into the cavity.

This is a divisional of copending application Ser. No. 08/660,184 filedon May 31, 1996 U.S. Pat. No. 5,795,799.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing anelectronic apparatus.

2. Description of the Related Art

Generally, in an electronic apparatus, components are mounted on bothfirst and second surfaces of a substrate, thus increasing the density ofmounted components. In this case, a cavity is provided on the firstsurface of the substrate, and a component is mounted on the firstsurface of the substrate within the cavity. Then, the apparatus isreversed, and another component is mounted on the second surface of thesubstrate. Note that, unless the cavity is provided on the surface ofthe substrate, it is impossible to reverse the apparatus.

In a first prior art method (see JP-A-3-211763), the substrate is madeof ceramic. Therefore, since the substrate is rigid, semiconductor chipsare mounted on both the first and second surfaces of the substrate andstable wire bonding operations are performed thereupon. Also, thesemiconductor chips are sealed by convex thermosetting resin envelopers.This will be explained later in detail.

In the first prior art method, however, in order to compensate for thefluctuation of height of the molded resin enveloper, the depth of thecavity is made large. As a result, a step between the molded resinenveloper and the first surface of the substrate becomes large. Thismakes it difficult to determine whether or not the appearance of themolded resin enveloper is bad, i.e., whether or not the molded resinenveloper is protruded from the cavity. Note that if the molded resinenveloper is protruded from the cavity, it is impossible to reverse theapparatus for preparing the wire bonding operation performed upon thesecond surface of the substrate. Also, the above-mentioned large stepincreases the size of the apparatus. Further, the ceramic substrate isheavy and expensive. Still further, it is difficult to mount thisapparatus on an organic mounting board which is broadly used, since adifference in thermal expansibility between the ceramic substrate andthe organic mounting board creates stress therebetween, so that cracksand disconnections may be generated in the ceramic substrate and theorganic mounting board as time passes.

In a second prior art method (see JP-A-5-259372) the substrate is madeof organic material. This also will be explained later in detail.

In the second prior art method, however, since the organic substrate isflexible, a stable wire bonding operation cannot be performed upon thesecond surface of the organic substrate. This reduces the density ofmounted chips.

Also, in the second prior art method, in order to compensate for thefluctuation of height of the molded resin enveloper, the depth of thecavity is made large. As a result, a step between the molded resinenveloper and the first surface of the substrate becomes large. Thismakes it difficult to determine whether or not the appearance of themolded resin enveloper is bad, i.e., whether or not the molded resinenveloper is protruded from the cavity.

Further, in the second prior art method, if the apparatus is large, adifference in thermal expansibility between the substrate and the moldedresin enveloper makes the apparatus warp, so that it is impossible toamount the apparatus on a mounting board.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method formanufacturing a small size electronic apparatus sealed by a molded resinenveloper in which it is easy to determine whether or not the appearanceof the molded resin enveloper is bad, and which increases the density ofmounted chips.

According to the present invention, in a method for manufacturing anelectronic apparatus, an electronic component is mounted on an organicsubstrate within its cavity. The electronic component is sealed by aconcave molded resin enveloper filled into the cavity. Thus, even if theorganic substrate is flexible, the combination of the organic substrateand the concave molded resin enveloper are rigid due to the concaveconfiguration thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more clearly understood from thedescription as set forth below, in comparison with the prior art, withreference to the accompanying drawings, wherein:

FIGS. 1A through 1E are cross-sectional views for explaining a firstprior art method for manufacturing an electronic apparatus;

FIGS. 2A through 2D are cross-sectional views for explaining a secondprior art method for manufacturing an electronic apparatus;

FIGS. 3A through 3F are cross-sectional views for explaining anembodiment of the method for manufacturing an electronic apparatusaccording to the present invention;

FIG. 4 is a cross-sectional view illustrating a modification of theapparatus of FIG. 3F; and

FIG. 5 is a cross-sectional view illustrating another modification ofthe apparatus of FIG. 3F.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Before the description of the preferred embodiment, prior art methodsfor manufacturing an electronic apparatus will be explained withreference to FIGS. 1A through 1E and FIGS. 2A through 2D.

FIGS. 1A through 1E illustrate a first prior art method formanufacturing an electronic apparatus (see JPA-3-211763).

First, referring to FIG. 1A, a ceramic substrate 1 having first andsecond surfaces is provided, and a cavity 2 is formed in the firstsurface of the ceramic substrate 1. An electrode pattern 3 is formed onthe first surface of the ceramic substrate 1, and an electrode pattern3' is formed on the second surface of the ceramic substrate 1.

Next, referring to FIG. 1B, a semiconductor chip 4 is mounted within thecavity 2 on the first surface of the ceramic substrate 1 by conductiveor insulating adhesives, and wires 5 are bonded between the electrodepattern 3 and the semiconductor chip 4. Then, thermosetting resin isintroduced into the cavity 2 to seal the semiconductor chip 4 as well asthe wires 5. In this case, the surface of a molded resin enveloper 6 isconvex.

Next, referring to FIG. 1C, the apparatus is reversed. Then, asemiconductor chip 4' is mounted on the second surface of the ceramicsubstrate 1 by conductive or insulating adhesives (not shown), and wires5' are bonded between the electrode pattern 3' and the semiconductorchip 4'. Then, thermosetting resin is introduced onto second surface ofthe ceramic substrate 1 to seal the semiconductor chip 4' as well as thewires 5'. In this case, the surface of a molded resin enveloper 6' isalso convex.

Next, referring to FIG. 1D, the apparatus is again reversed, and a chipcapacitor 7 is mounted by soldering or conductive adhesives on the firstsurface of the ceramic substrate 1.

Finally, referring to FIG. 1E, the apparatus is again reversed, and achip capacitor 7' is mounted by soldering or conductive adhesives on thesecond surface of the ceramic substrate 1, thus completing theapparatus.

In the first prior art method as illustrated in FIGS. 1A through 1E,since the ceramic substrate 1 is rigid, a stable wire bonding operationcan be performed upon both the first and second surfaces of the ceramicsubstrate 1, so that the wires 5 and 5' are formed.

In the first prior art method, however, in order to compensate for thefluctuation of height of the molded resin enveloper 6, the depth of thecavity 2 is made large. As a result, a step between the molded resinenveloper 6 and the first surface of the ceramic substrate 1 becomeslarge. This makes it difficult to determine whether or not theappearance of the molded resin enveloper 6 is bad, i.e., whether or notthe molded resin enveloper 6 is protruded from the cavity 2. Also, thisincreases the size of the apparatus. Further, the ceramic substrate 1 isheavy and expensive. Still further, it is difficult to mount theapparatus of FIG. 1E on an organic mounting board which is broadly used,since a difference in thermal expansibility between the ceramicsubstrate 1 and the organic mounting board creates stress therebetween,so that cracks and disconnections may be generated in the ceramicsubstrate 1 and the organic mounting board as time passes.

FIGS. 2A through 2D illustrate a second prior art method formanufacturing an electronic apparatus (see JP-A-5-259372).

First, referring to FIG. 2A, an organic base substrate 1' having firstand second surfaces is provided, and a framed organic connectionsubstrate 1" is formed on the organic base substrate 1', thus forming acavity 2 in the first surface of the organic base substrate 1'. Anelectrode pattern 3 is formed on the first surface of the organic basesubstrate 1', and an electrode pattern 3' is formed on the secondsurface of the organic base substrate 1'. Also, the electrode patterns 3and 3' are connected-to an electrode pattern 3" formed on the organicconnection substrate 1".

Next, referring to FIG. 2B, a semiconductor chip 4 is mounted within thecavity 2 on the first surface of the organic base substrate 1' byconductive or insulating adhesives, and wires 5 are bonded between theelectrode pattern 3 and the semiconductor chip 4. Then, a chip capacitor7 is mounted by soldering or conductive adhesives on the first surfaceof the organic base substrate 1'.

Next, referring to FIG. 2C, thermosetting resin is introduced into thecavity 2 to seal the semiconductor chip 4 as well as the wires 5. Inthis case, the surface of a molded resin enveloper 6 is convex.

Finally, referring to FIG. 2D, the apparatus is reversed, and chipcapacitors 7' and 7" and a mold component 8 are mounted by soldering orthe like on the second surface of the organic base substrate 1', thuscompleting the apparatus.

In the second prior art method, however, since the organic basesubstrate 1' is flexible, a stable wire bonding operation can not beperformed upon the second surface of the organic base substrate 1', sothat the chip capacitors 7' and 7" and the molded component 8 can bemounted on the second surface of the organic base substrate 1', but asemiconductor chip cannot be mounted thereon. This reduces the densityof mounted chips.

Also, in the second prior art method, in order to compensate for thefluctuation of height of the molded resin enveloper 6, the depth of thecavity 2 is made large. As a result, a step between the molded resinenveloper 6 and the first surface of the organic base substrate 1'becomes large. This makes it difficult to determine whether or not theappearance of the molded resin enveloper 6 is good, and increases thesize of the apparatus. Further, if the apparatus of FIG. 2D is large, adifference in thermal expansibility between the substrate 1' and themolded resin enveloper 6 makes the apparatus of FIG. 2D warp, so that itis impossible to amount the apparatus of FIG. 2D on a mounting board.

FIGS. 3A through 3F illustrate an embodiment of the method formanufacturing an electronic apparatus according to the presentinvention.

First, referring FIG. 3A, in the same way as in FIG. 2A, an organic basesubstrate 1' having first and second surfaces is provided, and an about0.1 to 1 mm thick framed organic connection substrate 1" is formed onthe organic base substrate 1', thus forming a cavity 2 in the firstsurface of the organic base substrate 1'. An electrode pattern 3 isformed on the first surface of the organic base substrate 1', and anelectrode pattern 3' is formed on the second surface of the organic basesubstrate 1'. Also, the electrode patterns 3 and 3' are connected to anelectrode pattern 3" formed on the organic connection substrate 1". Notethat the organic base substrate 1' and the organic connection substrate1" are made of the same material such as glass-expoxy, and thus there islittle stress between the organic base substrate 1' and the organicconnection substrate 1".

Next, referring to FIG. 3B, in the same way as in FIG. 2B, asemiconductor chip 4 is mounted within the cavity 2 on the first surfaceof the organic base substrate 1' by conductive or insulating adhesives(not shown), and wires 5 are bonded between the electrode pattern 3 andthe semiconductor chip 4. Then, a chip capacitor 7 is mounted bysoldering or conductive adhesives on the first surface of the organicbase substrate 1'. Note, that a difference in height between the organicconnection substrate 1" and the wires 5 is about 0.1 to 0.5 mm.

Next, referring to FIG. 3C, liquid thermosetting epoxy resin isintroduced from a dispensing needle 9 into the cavity 2 from peripheralportion thereof to seal the semiconductor chip 4 as well as the wires 5and the chip capacitor 7. In this case, the capacity of introduced resinis a little smaller than the cavity 2, and the viscosity of the resin islow so that the surface tension of the resin makes the surface thereofconcave. Thereafter, the resin is heated and hardened as shown in FIG.3D. In this case, the flexual modulus of a molded resin enveloper 6 islarger than 100 kg/mm², and therefore, the molded resin enveloper 6hardly cracks even at a wire bonding operation temperature. In thiscase, the height of the organic connection substrate 1" is about 0.1 to1 mm, and a difference in height between the maximum height of the wires5 and the chip capacitor 7 and the organic connection substrate 1" isabout 0.1 to 0.5 mm.

Next, referring to FIG. 3E, the apparatus is reversed. Then, asemiconductor chip 4' is mounted on the second surface of the organicbase substrate 1' by conductive adhesives, and wires 5' are bondedbetween the electrode pattern 3' and the semiconductor chip 4'. In thiscase, the apparatus is located on a stage 10. Then, a chip capacitor 7'is mounted by soldering or conductive adhesives on the second surface ofthe organic base substrate 1'.

Finally, referring to FIG. 3F, a frame 11 made of glass-epoxy or thelike is mounted on the second surface of the organic base substrate 1'.The configuration of the frame 11 is almost the same as that the organicconnection substrate 1". Then, thermosetting resin is introduced ontothe second surface of the organic base substrate 1' to seal thesemiconductor chip 4' as well as the wires 5' and the chip capacitor 7',thus completing the apparatus. In this case, the surface of the moldedresin enveloper 6' is almost flat at its center portion. Note that themolded resin enveloper 6' is made of the same material of the moldedregin enveloper 6, so that a difference in thermal expansibilitytherebetween is almost zero. Thus, the apparatus hardly warps.

Thus, in the embodiment, even when the organic base substrate 1' isused, the combination of the organic base substrate 1' and the organicconnection substrate 1" are rigid due to the concave configuration ofthe molded resin enveloper 6. AS a result, the apparatus can be locatedon the stage 10 as illustrated in FIG. 5E, and a stable wire bondingoperation can be performed upon the second surface of the organic basesubstrate 1'. This increases the density of mounted chips.

Also, in the embodiment, since the apparatus is almost symmetrical withrespect to its longitudinal direction, the apparatus hardly warps sothat it is easy to mount the apparatus on a mounting board.

Further, in the embodiment, since the molded resin enveloper 6 isconcave, it is easy to determine whether or not the appearance of themolded resin enveloper 6 is bad, i.e., whether or not the molded resinenveloper 6 is protruded from the cavity 2. Therefore, the fluctuationof height of the molded resin enveloper 6 can be reduced, andaccordingly, the depth of the cavity 2 can be reduced, thus reducing thesize of the apparatus.

In FIG. 4, which illustrates a modification of the apparatus of FIG. 3F,the semiconductor chip 4' as well as the bonding wires 5' and the chipcapacitor 7' are sealed by transfer molding using a thermoplastic resinenveloper 12, instead of the thermosetting resin enveloper 6' and theframe 11 of FIG. 3F. That is, the apparatus of FIG. 3E is sandwiched bytwo metal molds (not shown). Then, hot thermoplastic resin is injectedinto a cavity between the metal molds, and the injected thermoplasticresin is cooled and hardened by the metal molds. Thus, a thermoplasticresin enveloper 12 is formed. Further, the electrode patterns 3 and 3'are connected hemispherical solder balls 3a and 3a', thus forming a ballgrid array (BGA). Note that the enveloper 12 can be made ofthermosetting resin.

In FIG. 5, which illustrates another modification of the apparatus ofFIG. 3F, a mold component 8 instead of the semiconductor chip 4' of FIG.3F is mounted on the second surface of the organic base substrate 1'. Inthis case, a small frame 11" is provided to surround the mold component8, and the mold component 8 is sealed by a thermosetting resin enveloper6'. Note that the apparatus is easily sucked by the nozzles (not shown),since the frame 11" is small.

As explained hereinabove, according to the present invention, since anorganic substrate having a cavity is sealed by a concave molded resinenveloper, it is easy to determine whether or not the appearance of themolded resin enveloper is bad. Therefore,the molded resin enveloper canbe thin, and accordingly the depth of the cavity can be reduced, thusreducing the size of the apparatus. Also, the organic substrate having acavity can be rigid due to the concave configuration of molded resin inthe cavity, stable wire bonding operation can be performed upon bothsurfaces of the organic substrate. Further, the density of mounted chipscan be increased.

What is claimed is:
 1. An electronic apparatus comprising:an organicbase substrate having first and second surfaces; first and secondelectrode patterns formed on said first and second surfaces,respectively; a first frame formed on said first surface; a firstsemiconductor chip mounted on said first surface and connected by wiresto said first electrode pattern; a concave molded resin enveloper formedon said first semiconductor chip within said first frame; a second frameformed on said second surface; a second semiconductor chip mounted onsaid second surface and connected by wires to said second electrodepattern; and an approximately flat molded resin enveloper formed on saidsecond semiconductor chip within said second frame.
 2. The apparatus asset forth in claim 1, wherein said concave molded resin enveloper andsaid flat molded resin enveloper are made of a common material.
 3. Anelectronic apparatus comprising:an organic base substrate having firstand second surfaces; first and second electrode patterns formed on saidfirst and second surfaces, respectively; a first frame formed on saidfirst surface; a first semiconductor chip mounted on said first surfaceand connected by wires to said first electrode pattern; a concave moldedresin enveloper formed on said semiconductor chip within said firstframe; a second frame formed on said second surface; a mold componentmounted on said second surface and connected to said second electrodepattern; and an approximately flat molded resin enveloper formed on saidmold component within said second frame.
 4. The apparatus as set forthin claim 3, wherein said concave molded resin enveloper and raid flatmolded resin enveloper are made of a common material.